NIST provides key measurements for superconducting magnets for the International Thermonuclear Experimental Reactor.Superconducting magnets are used in fusion energy projects, such as the International Thermonuclear ther·mo·nu·cle·ar adj. 1. Of, relating to, or derived from the fusion of atomic nuclei at high temperatures: thermonuclear reactions. 2. Experimental Reactor (ITER ITER. A foot way. Vide Way. ), to confine and heat the plasma. The superconductors for the ITER's large magnet systems are all "cable-in-conduit conductors" (CICC CICC Custom Integrated Circuits Conference CICC Center for the Improvement of Child Caring (Studio City, CA) CICC China International Capital Corp. ), which provide both mechanical support for the large magnetic forces and a flow path for the liquid helium required to cool the cable. The superconducting magnet must be operated below the critical current of the cable, which is a function of magnetic field and temperature. Temperature is an important variable, and the local temperature of the conductor depends on the mass-flow rate of the coolant coolant (kōō´l  nt),n and the distribution of the heat load along the CICC. Earlier magnet systems that used CICC experienced unexpected degradation of their superconducting properties. To help determine the source of such degradation, NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. scientists measured variable-temperature critical current of a "witness" superconductor A material that has little resistance to the flow of electricity. Traditional superconductors operate at absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius). Experiments in the 1980s raised the temperature to -321 degrees Fahrenheit. strand that was thermally processed along with the superconducting cables used to make the latest two ITER test conductors. The results of NIST's unique variable-temperature measurements provide a comprehensive mapping of critical current as a function of magnetic field (0 T to 12 T) and temperature (4 K to 17 K), and form a basis for evaluating CICC and magnet performance. NIST scientists used the data to generate curves of electric field versus temperature at constant current and magnetic field. These, in turn, gave a direct indication of the temperature safety margin of the conductor. NIST's results will be used by Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory: see Lawrence Berkeley National Laboratory. (body) Lawrence Livermore National Laboratory - (LLNL) A research organaisatin operated by the University of California under a contract with the US Department of Energy. , which will test CICC samples at the Plasma Physics Research Center in Villigen, Switzerland, with current up to 100 000 A and magnetic fields up to 12 T, while controlling the mass-flow rate of the coolant. More information about ITER may be found at www.iter.org. CONTACT: Ron Goldfarb, (303) 497-3650; goldfarb@boulder.nist.gov. |
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